The invention relates to an intake system for internal-combustion engines supercharged in one or two stages in which taken-in combustion air, is led from the compressors of the exhaust gas turbochargers through interposed charge air coolers to an air collecting housing of the internal-combustion engine and finally from there to the inlet ducts of the cylinder heads of the internal-combustion engine.
An intake system of this general type is known from the German Patent Document DE-OS 20 59 220. In the case of this internal-combustion engine with a V-shaped arrangement of the cylinders in two banks, an exhaust gas turbocharger is assigned to each cylinder bank for the one-stage charging. The combustion air, which is compressed by the compressors, arrives in collecting pipes extending along the internal-combustion engine in which the charge air coolers are integrated. By means of a series connection of several block-shaped heat exchanger elements, a low overall height of the collecting pipes is achieved. It is not indicated, however, how a space-saving arrangement of an intake system is to be designed with exhaust gas turbochargers, charge air coolers and collecting housings at constructional expenditures that are as low as possible when the internal-combustion engine is to be changed into an internal-combustion engine which is supercharged in two stages.
The instant invention is based on the object of providing an intake system which, while only a few different components are used, can be used for a one-stage as well as for a two-stage supercharging, and as a result offers logistical advantages, which, in addition, makes it possible to render the dimensions of the engine variants and the mounting of the intake systems largely uniform, and which is also favorable with respect to air flow guiding.
This object is achieved in the case of a construction of the intake system for use in one-stage or two-stage supercharging, of having at least one exhaust gas turbocharger, one charge air cooler and one air collecting housing, with connecting pipes therebetween and to the inlet ducts of the cylinder heads. Accordingly, the exhaust gas turbochargers, the charge air coolers and the air collecting housings as well as the pipes to the inlet ducts of the cylinder heads are used in the same arrangement in one-stage supercharging as in two-stage supercharging. Naturally, in the case of a two-stage supercharging, a low-pressure charge air cooler must be added. Instead of the charge air cooler used in the case of the one-stage supercharging, a high-pressure charge air cooler is provided. And instead of the exhaust gas turbochargers used in a one-stage supercharging, high-pressure exhaust gas turbochargers are provided. In one-stage supercharging, the flow housing forms an intake housing with an intake funnel, and in the two-stage supercharging, the flow housing encloses the cooling element of the low-pressure charge air cooler. Both flow housings are constructed with an identical bottom part which is arranged at the same point on the engine in one-stage and in two-stage supercharging. This standardization leads to logistical advantages with a corresponding cost reduction. The assembly is simplified and the space requirement is similar in the case of the one-stage and two-stage supercharging. The intake system is also favorable with respect to air flow guiding. A particularly low space requirement and an optimal flow guidance with a good distribution of the flow to the cylinders is obtained if the air collecting housing extends between cylinder banks arranged in a V-shape along the internal-combustion engine and if system parts can be arranged on the top side of the air collecting housing. In one-stage supercharging, an intake funnel and a charge air cooler are arranged next to one another on the air collecting housing. In two-stage supercharging, a high-pressure charge air cooler and a low-pressure charge air cooler are arranged next to one another on the air collecting housing. Having the exhaust gas turbochargers on a narrow side of the air collecting housing and a bottom part of the housing having connection tubes situated directly opposite the inlets of the compressors, further reduces the space requirement and is particularly advantageous with respect to air flow guidance. The intake system has an upper wall boundary of the air collecting housing in a tub-shaped construction so that a flow space is formed by which air reaches the molded-on connection tube connected with the intake connections of the compressors. In multi-stage supercharging, one exhaust gas turbocharger is normally assigned to each cylinder bank. In the case of a two-stage supercharging, an exhaust gas turbocharger group is assigned to each cylinder bank. In the case of a partial engine load, when a low amount of exhaust gas is available, the exhaust gas ejected by the two cylinder banks is used to drive only one charger or one group of exhaust gas turbochargers. The exhaust gas pipe leading to the turbine and the intake pipe of a corresponding exhaust gas turbocharger leading to the compressor are therefore equipped with shut-off devices which are actuated for the shutting-off of the exhaust gas turbocharger. In one-stage supercharging, the compressor-side shut-off device is advantageously arranged at the inlet of the intake funnel because such a location is easily accessible for servicing operations. In this arrangement, the flow ducts must be separated inside the intake funnel. A transverse wall is therefore provided in the intake funnel which, together with webs in the tub-shaped bottom part of the housing, form separate intake ducts for the two intake connections of the compressors. In a two-stage supercharging with two exhaust gas turbocharger groups assigned to the two cylinder banks and with a switching-off of one exhaust gas turbocharger group at partial load, it is also necessary to separate the intake ducts in the intercooler. For this reason, two separate heat exchanger elements are used which are separated by a transverse wall in the housing. This transverse wall, together with the webs in the tub-shaped flow space disposed underneath, forms separate flow ducts for the exhaust gas turbochargers respectively assigned to each cylinder bank. The tub-shaped flow space (molded to the air collecting housing with webs for separate flow ducts) may therefore be maintained unchanged in one-stage, two-stage or multi-stage supercharging. In addition, to provide for a space-saving construction, the housing of the charge air cooler is constructed as a lid for the air collecting housing. The charge air is introduced into the housings of the charge air coolers by way of lateral inlets situated on the top.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.